Hypothermia is a condition of subnormal body temperature and presents serious consequences to the patient suffering therefrom. It has been shown that nearly seventy five percent of all patients who undergo surgical procedures develop hypothermia. This equates to approximately fourteen million patients a year in the United States alone. The hypothermic condition is brought on by many factors including anesthesia, the air conditioning of the operating room, and the infusion of cold blood, I-V solutions, or irrigating fluids.
Several methods and products have been developed to help prevent hypothermia from occurring; such as the use of infrared lamps, cotton blankets, and warm water mattresses. However, none of these methods and products have proven completely successful. In fact, it has been shown that these methods and products can not even prevent the patients from losing their endogenous heat. (See Journal of Post Anesthesia Nursing, Vol. 5, No. 4, August 1990, pp 254-263).
Another method of helping to prevent hypothermia that has proven very effective is the use of forced warm air convection. As early as 1937, a refrigeration blanket using cold air convection was suggested in U.S. Pat. No. 2,093,834 to Gaugler. This blanket included a plurality of layers for channeling airflow from an inlet port. Non-inflatable portions were provided around the periphery of the blanket to secure the blanket around the body. Gaugler does not mention hypothermia treatment and does not suggest that the blanket could be used to supply warm air.
U.S. Pat. No. 2,512,559 to Williams also relates to a blanket for providing cooled air to a person. The blanket in Williams comprised a plurality of thin sheets of material connected together at a plurality of discrete locations and connected together in a continuous line about the peripheral edge. An air inlet was provided to communicate with space between the sheets to allow cool air to be supplied thereto. Again, no mention of hypothermia treatment or the supply of warm air is made.
In U.S. Pat. No. 4,572,188 to Augustine, et al., a forced air convection system which can supply either cool or warm air to a blanket is described. The blanket in Augustine, et al. comprises a plurality of inflatable hollow tubes having their interiors connected together through transverse openings. An entry port is provided in the upper surface of the blanket for admitting the cool or warm air and small exit ports are provided through the lower surface to allow the cool or warm air to flow out toward a body covered by the blanket.
Other patents relating to the supply of cool or warm air to a person through an inflatable blanket include U.S. Pat. No. 4,660,388 to Greene, Jr.; U.S. Pat. No. 4,777,802 to Feher; and U.S. Pat. No. 4,867,230 to Voss. Each of these patents describe blankets having various attributes and configurations to supply cool or warm air to the person.
While there are a number of patents noted above and others not mentioned which relate to inflatable blankets for use in supplying cool or warm air to a patient, there remains a need in the art for improvements to forced air convection systems.